The availability of relatively inexpensive, low-error, and high-bandwidth communication plays a prominent role in creating and maintaining today's information-oriented economy. Wireless communications in particular provide an omnipresent capability to exchange ideas and information. In a wireless communication exchange, electromagnetic radiation is transmitted from one device and received at another. Each device usually transmits and receives electromagnetic signals during a given communication exchange.
The electromagnetic signals are typically propagated between two devices over the air. The electromagnetic signals are transferred to and from the air medium using an antenna. Hence, the antenna acts as a bridge between the device and the transmission medium. Although electromagnetic signals travel at one basic speed, they have different wavelengths and frequencies. Different antennas are adept at interacting with electromagnetic signals of different frequency ranges or bandwidths.
Wireless communication is controlled by different wireless standards and/or governmental regulations. These standards and regulations assign particular types of communications to different frequency bandwidths. Being able to communicate in different frequency bandwidths can increase wireless options in certain communication scenarios. Consequently, many devices today can operate in more than one frequency band.
To properly communicate in multiple frequency bands, such devices often include an antenna for each desired frequency band. Alternatively, designers often try to cover two or more bands with a single antenna. This often leads to a number of compromises, including those related to antenna size, transceiver complexity, and overall communication performance.
One multi-band antenna design was presented by M. John, M. J. Ammann, and R. Farrell in a paper entitled “Printed Triband Terminal Antenna”; IEE Conf., Wideband and Multiband Antennas and Arrays; Birmingham, 2005; pages 19-23. These authors refer to their antenna as a “printed triple-band multibranch monopole.” A version of their triband antenna is depicted in FIG. 1.
FIG. 1 depicts a triband antenna assembly 101 in accordance with an existing design presented by John, Ammann, and Farrell. As illustrated, triband antenna assembly 101 includes a microstrip feedline 103, a groundplane 105, and a multibranch monopole 107. Microstrip feedline 103 and multibranch monopole 107 are located on the front of a substrate of triband antenna assembly 101. Groundplane 105 may be square and is located on the back of the substrate.
Multibranch monopole 107 includes three monopole branches 107a, 107b, and 107c. Microstrip feedline 103, monopole branch 107a, monopole branch 107b, and monopole branch 107c form a “plus-shaped” junction. Monopole branch 107b extends from the plus-shaped junction parallel to microstrip feedline 103 in an apparent extension thereof. Monopole branch 107b is straight. Monopole branch 107a and monopole branch 107c extend from the plus-shaped junction perpendicular to microstrip feedline 103. Each of monopole branch 107a and monopole branch 107c includes one bend.
According to the authors, this triband antenna assembly 101 is designed to operate in three bands. However, this antenna is larger than is suitable for all applications and frequency bands that may be desirable (e.g., it may be too large for some portable devices and purposes). Moreover, drawbacks relating to having a plus-shaped junction, which are explained further herein below, have been discovered by the inventor of the instant patent application.